Factor out strict implementations of transformation operations.

Add StrictOptimizedMapOps and StrictOptimizedSortedMapOps.

Only operations that were implemented more than once have been factored
out. Some other operations could be factored out so that they could
be reused by custom collection implementations.

Fixes scala/collection-strawman#325

src/library/scala/collection/StrictOptimizedIterableOps.scala

@@ -5,9 +5,10 @@ import scala.annotation.unchecked.uncheckedVariance
 import scala.language.higherKinds
 
 /**
-  * Trait that overrides operations to take advantage of strict builders.
+  * Trait that overrides iterable operations to take advantage of strict builders.
   *
   * @tparam A  Elements type
+  * @tparam CC Collection type constructor
   * @tparam C  Collection type
   */
 trait StrictOptimizedIterableOps[+A, +CC[_], +C]
@@ -70,54 +71,23 @@ trait StrictOptimizedIterableOps[+A, +CC[_], +C]
   // the view-based implementations, but they turn out to be slightly faster because
   // a couple of indirection levels are removed
 
-  override def map[B](f: A => B): CC[B] = {
-    val b = iterableFactory.newBuilder[B]
-    val it = iterator
-    while (it.hasNext) {
-      b += f(it.next())
-    }
-    b.result()
-  }
+  override def map[B](f: A => B): CC[B] =
+    StrictOptimizedOps.map(iterator, iterableFactory.newBuilder, f)
 
-  override def flatMap[B](f: A => IterableOnce[B]): CC[B] = {
-    val b = iterableFactory.newBuilder[B]
-    val it = iterator
-    while (it.hasNext) {
-      b ++= f(it.next())
-    }
-    b.result()
-  }
+  override def flatMap[B](f: A => IterableOnce[B]): CC[B] =
+    StrictOptimizedOps.flatMap(iterator, iterableFactory.newBuilder, f)
 
-  override def collect[B](pf: PartialFunction[A, B]): CC[B] = {
-    val b = iterableFactory.newBuilder[B]
-    val it = iterator
-    while (it.hasNext) {
-      val elem = it.next()
-      if (pf.isDefinedAt(elem)) {
-        b += pf.apply(elem)
-      }
-    }
-    b.result()
-  }
+  override def concat[B >: A](suffix: Iterable[B]): CC[B] =
+    StrictOptimizedOps.concat(iterator, suffix.iterator, iterableFactory.newBuilder[B])
 
-  override def flatten[B](implicit toIterableOnce: A => IterableOnce[B]): CC[B] = {
-    val b = iterableFactory.newBuilder[B]
-    val it = iterator
-    while (it.hasNext) {
-      b ++= toIterableOnce(it.next())
-    }
-    b.result()
-  }
+  override def collect[B](pf: PartialFunction[A, B]): CC[B] =
+    StrictOptimizedOps.collect(iterator, iterableFactory.newBuilder, pf)
 
-  override def zip[B](that: Iterable[B]): CC[(A @uncheckedVariance, B)] = {
-    val b = iterableFactory.newBuilder[(A, B)]
-    val it1 = iterator
-    val it2 = that.iterator
-    while (it1.hasNext && it2.hasNext) {
-      b += ((it1.next(), it2.next()))
-    }
-    b.result()
-  }
+  override def flatten[B](implicit toIterableOnce: A => IterableOnce[B]): CC[B] =
+    StrictOptimizedOps.flatten(iterator, iterableFactory.newBuilder)
+
+  override def zip[B](that: Iterable[B]): CC[(A @uncheckedVariance, B)] =
+    StrictOptimizedOps.zip(iterator, that.iterator, iterableFactory.newBuilder[(A, B)])
 
   override def zipWithIndex: CC[(A @uncheckedVariance, Int)] = {
     val b = iterableFactory.newBuilder[(A, Int)]

src/library/scala/collection/StrictOptimizedMapOps.scala

@@ -0,0 +1,29 @@
+package scala.collection
+
+import scala.language.higherKinds
+
+/**
+  * Trait that overrides map operations to take advantage of strict builders.
+  *
+  * @tparam K  Type of keys
+  * @tparam V  Type of values
+  * @tparam CC Collection type constructor
+  * @tparam C  Collection type
+  */
+trait StrictOptimizedMapOps[K, +V, +CC[_, _] <: IterableOps[_, AnyConstr, _], +C]
+  extends MapOps[K, V, CC, C]
+    with StrictOptimizedIterableOps[(K, V), Iterable, C] {
+
+  override def map[K2, V2](f: ((K, V)) => (K2, V2)): CC[K2, V2] =
+    StrictOptimizedOps.map(iterator, mapFactory.newBuilder, f)
+
+  override def flatMap[K2, V2](f: ((K, V)) => IterableOnce[(K2, V2)]): CC[K2, V2] =
+    StrictOptimizedOps.flatMap(iterator, mapFactory.newBuilder, f)
+
+  override def concat[V2 >: V](suffix: Iterable[(K, V2)]): CC[K, V2] =
+    StrictOptimizedOps.concat(iterator, suffix.iterator, mapFactory.newBuilder)
+
+  override def collect[K2, V2](pf: PartialFunction[(K, V), (K2, V2)]): CC[K2, V2] =
+    StrictOptimizedOps.collect(iterator, mapFactory.newBuilder, pf)
+
+}

src/library/scala/collection/StrictOptimizedOps.scala

@@ -0,0 +1,109 @@
+package scala.collection
+
+/**
+  * Convenient implementations of transformation operations
+  * based on builders.
+  *
+  * All the methods defined here are expected to be called with
+  * freshly created iterators and builders.
+  */
+object StrictOptimizedOps {
+
+  /**
+    * @param it Iterator to map elements from
+    * @param b Builder to use to build the resulting collection
+    * @param f Element transformation function
+    * @tparam A Type of elements of the source collection (e.g. `Int`)
+    * @tparam B Type of elements of the resulting collection (e.g. `String`)
+    * @tparam C Type of the resulting collection (e.g. `List[String]`)
+    * @return The resulting collection
+    */
+  @inline def map[A, B, C](it: Iterator[A], b: mutable.Builder[B, C], f: A => B): C = {
+    while (it.hasNext) {
+      b += f(it.next())
+    }
+    b.result()
+  }
+
+  /**
+    * @param it Iterator to flatMap elements from
+    * @param b Builder to use to build the resulting collection
+    * @param f Element transformation function
+    * @tparam A Type of elements of the source collection (e.g. `Int`)
+    * @tparam B Type of elements of the resulting collection (e.g. `String`)
+    * @tparam C Type of the resulting collection (e.g. `List[String]`)
+    * @return The resulting collection
+    */
+  @inline def flatMap[A, B, C](it: Iterator[A], b: mutable.Builder[B, C], f: A => IterableOnce[B]): C = {
+    while (it.hasNext) {
+      b ++= f(it.next())
+    }
+    b.result()
+  }
+
+  /**
+    * @param it1 Iterator of the first collection
+    * @param it2 Iterator of the second collection
+    * @param b Builder to use to build the resulting collection
+    * @tparam A Type of elements (e.g. `Int`)
+    * @tparam C Type of the resulting collection (e.g. `List[Int]`)
+    * @return The resulting collection
+    */
+  @inline def concat[A, C](it1: Iterator[A], it2: Iterator[A], b: mutable.Builder[A, C]): C = {
+    b ++= it1
+    b ++= it2
+    b.result()
+  }
+
+  /**
+    * @param it Iterator to collect elements from
+    * @param b Builder to use to build the resulting collection
+    * @param pf Element transformation partial function
+    * @tparam A Type of elements of the source collection (e.g. `Int`)
+    * @tparam B Type of elements of the resulting collection (e.g. `String`)
+    * @tparam C Type of the resulting collection (e.g. `List[String]`)
+    * @return The resulting collection
+    */
+  @inline def collect[A, B, C](it: Iterator[A], b: mutable.Builder[B, C], pf: PartialFunction[A, B]): C = {
+    while (it.hasNext) {
+      val elem = it.next()
+      if (pf.isDefinedAt(elem)) {
+        b += pf.apply(elem)
+      }
+    }
+    b.result()
+  }
+
+  /**
+    * @param it Iterator to flatten elements from
+    * @param b Builder to use to build the resulting collection
+    * @param toIterableOnce Evidence that `A` can be seen as an `IterableOnce[B]`
+    * @tparam A Type of elements of the source collection (e.g. `List[Int]`)
+    * @tparam B Type of elements of the resulting collection (e.g. `Int`)
+    * @tparam C Type of the resulting collection (e.g. `List[Int]`)
+    * @return The resulting collection
+    */
+  @inline def flatten[A, B, C](it: Iterator[A], b: mutable.Builder[B, C])(implicit toIterableOnce: A => IterableOnce[B]): C = {
+    while (it.hasNext) {
+      b ++= toIterableOnce(it.next())
+    }
+    b.result()
+  }
+
+  /**
+    * @param it1 Iterator of the first collection
+    * @param it2 Iterator of the second collection
+    * @param b Builder to use to build the resulting collection
+    * @tparam A Type of elements of the first collection (e.g. `Int`)
+    * @tparam B Type of elements of the second collection (e.g. `String`)
+    * @tparam C Type of the resulting collection (e.g. `List[(Int, String)]`)
+    * @return The resulting collection
+    */
+  @inline def zip[A, B, C](it1: Iterator[A], it2: Iterator[B], b: mutable.Builder[(A, B), C]): C = {
+    while (it1.hasNext && it2.hasNext) {
+      b += ((it1.next(), it2.next()))
+    }
+    b.result()
+  }
+
+}

src/library/scala/collection/StrictOptimizedSeqOps.scala

@@ -8,8 +8,8 @@ import scala.language.higherKinds
   */
 trait StrictOptimizedSeqOps [+A, +CC[_], +C]
   extends Any
-    with SeqOps[A, CC, C]
-    with StrictOptimizedIterableOps[A, CC, C] {
+    with StrictOptimizedIterableOps[A, CC, C]
+    with SeqOps[A, CC, C] {
 
   override def distinctBy[B](f: A => B): C = {
     val builder = newSpecificBuilder
@@ -45,12 +45,8 @@ trait StrictOptimizedSeqOps [+A, +CC[_], +C]
     b.result()
   }
 
-  override def appendedAll[B >: A](suffix: Iterable[B]): CC[B] = {
-    val b = iterableFactory.newBuilder[B]
-    b ++= this
-    b ++= suffix
-    b.result()
-  }
+  override def appendedAll[B >: A](suffix: Iterable[B]): CC[B] =
+    StrictOptimizedOps.concat(iterator, suffix.iterator, iterableFactory.newBuilder)
 
   override def prependedAll[B >: A](prefix: Iterable[B]): CC[B] = {
     val b = iterableFactory.newBuilder[B]

src/library/scala/collection/StrictOptimizedSetOps.scala

@@ -0,0 +1,17 @@
+package scala.collection
+
+/**
+  * Trait that overrides set operations to take advantage of strict builders.
+  *
+  * @tparam A  Elements type
+  * @tparam CC Collection type constructor
+  * @tparam C  Collection type
+  */
+trait StrictOptimizedSetOps[A, +CC[_], +C <: SetOps[A, CC, C]]
+  extends SetOps[A, CC, C]
+    with StrictOptimizedIterableOps[A, CC, C] {
+
+  override def concat(that: Iterable[A]): C =
+    StrictOptimizedOps.concat(iterator, that.iterator, newSpecificBuilder)
+
+}

src/library/scala/collection/StrictOptimizedSortedMapOps.scala

@@ -0,0 +1,27 @@
+package scala.collection
+
+/**
+  * Trait that overrides sorted map operations to take advantage of strict builders.
+  *
+  * @tparam K  Type of keys
+  * @tparam V  Type of values
+  * @tparam CC Collection type constructor
+  * @tparam C  Collection type
+  */
+trait StrictOptimizedSortedMapOps[K, +V, +CC[X, Y] <: Map[X, Y] with SortedMapOps[X, Y, CC, _], +C <: SortedMapOps[K, V, CC, C]]
+  extends SortedMapOps[K, V, CC, C]
+    with StrictOptimizedMapOps[K, V, Map, C] {
+
+  override def map[K2, V2](f: ((K, V)) => (K2, V2))(implicit ordering: Ordering[K2]): CC[K2, V2] =
+    StrictOptimizedOps.map(iterator, sortedMapFactory.newBuilder, f)
+
+  override def flatMap[K2, V2](f: ((K, V)) => IterableOnce[(K2, V2)])(implicit ordering: Ordering[K2]): CC[K2, V2] =
+    StrictOptimizedOps.flatMap(iterator, sortedMapFactory.newBuilder, f)
+
+  override def concat[V2 >: V](xs: Iterable[(K, V2)]): CC[K, V2] =
+    StrictOptimizedOps.concat(iterator, xs.iterator, sortedMapFactory.newBuilder)
+
+  override def collect[K2, V2](pf: PartialFunction[(K, V), (K2, V2)])(implicit ordering: Ordering[K2]): CC[K2, V2] =
+    StrictOptimizedOps.collect(iterator, sortedMapFactory.newBuilder, pf)
+
+}

src/library/scala/collection/StrictOptimizedSortedSetOps.scala

@@ -5,48 +5,27 @@ package collection
 import scala.annotation.unchecked.uncheckedVariance
 import scala.language.higherKinds
 
+/**
+  * Trait that overrides sorted set operations to take advantage of strict builders.
+  *
+  * @tparam A  Elements type
+  * @tparam CC Collection type constructor
+  * @tparam C  Collection type
+  */
 trait StrictOptimizedSortedSetOps[A, +CC[X] <: SortedSet[X], +C <: SortedSetOps[A, CC, C]]
   extends SortedSetOps[A, CC, C]
-    with StrictOptimizedIterableOps[A, Set, C] {
-
-  override def map[B : Ordering](f: A => B): CC[B] = {
-    val b = sortedIterableFactory.newBuilder[B]
-    val it = iterator
-    while (it.hasNext) {
-      b += f(it.next())
-    }
-    b.result()
-  }
-
-  override def flatMap[B : Ordering](f: A => IterableOnce[B]): CC[B] = {
-    val b = sortedIterableFactory.newBuilder[B]
-    val it = iterator
-    while (it.hasNext) {
-      b ++= f(it.next())
-    }
-    b.result()
-  }
-
-  override def zip[B](that: Iterable[B])(implicit ev: Ordering[(A @uncheckedVariance, B)]): CC[(A @uncheckedVariance, B)] = { // sound bcs of VarianceNot
-    val b = sortedIterableFactory.newBuilder[(A, B)]
-    val it1 = iterator
-    val it2 = that.iterator
-    while (it1.hasNext && it2.hasNext) {
-      b += ((it1.next(), it2.next()))
-    }
-    b.result()
-  }
-
-  override def collect[B : Ordering](pf: PartialFunction[A, B]): CC[B] = {
-    val b = sortedIterableFactory.newBuilder[B]
-    val it = iterator
-    while (it.hasNext) {
-      val elem = it.next()
-      if (pf.isDefinedAt(elem)) {
-        b += pf.apply(elem)
-      }
-    }
-    b.result()
-  }
+    with StrictOptimizedSetOps[A, Set, C] {
+
+  override def map[B : Ordering](f: A => B): CC[B] =
+    StrictOptimizedOps.map(iterator, sortedIterableFactory.newBuilder, f)
+
+  override def flatMap[B : Ordering](f: A => IterableOnce[B]): CC[B] =
+    StrictOptimizedOps.flatMap(iterator, sortedIterableFactory.newBuilder, f)
+
+  override def zip[B](that: Iterable[B])(implicit ev: Ordering[(A @uncheckedVariance, B)]): CC[(A @uncheckedVariance, B)] =
+    StrictOptimizedOps.zip(iterator, that.iterator, sortedIterableFactory.newBuilder[(A, B)])
+
+  override def collect[B : Ordering](pf: PartialFunction[A, B]): CC[B] =
+    StrictOptimizedOps.collect(iterator, sortedIterableFactory.newBuilder, pf)
 
 }

src/library/scala/collection/immutable/BitSet.scala

@@ -22,7 +22,8 @@ sealed abstract class BitSet
     with collection.BitSet
     with SortedSetOps[Int, SortedSet, BitSet]
     with collection.BitSetOps[BitSet]
-    with StrictOptimizedIterableOps[Int, Set, BitSet] {
+    with StrictOptimizedIterableOps[Int, Set, BitSet]
+    with StrictOptimizedSortedSetOps[Int, SortedSet, BitSet] {
 
   def bitSetFactory = BitSet
 

src/library/scala/collection/immutable/ChampHashMap.scala

@@ -3,7 +3,7 @@ package collection.immutable
 
 import java.io.{ObjectInputStream, ObjectOutputStream}
 
-import collection.{IterableFactory, Iterator, MapFactory, StrictOptimizedIterableOps}
+import collection.{IterableFactory, Iterator, MapFactory, StrictOptimizedIterableOps, StrictOptimizedMapOps}
 import collection.Hashing.{computeHash, keepBits}
 import scala.annotation.unchecked.{uncheckedVariance => uV}
 import java.lang.Integer.bitCount
@@ -26,7 +26,8 @@ import scala.collection.mutable.{Builder, ImmutableBuilder}
 final class ChampHashMap[K, +V] private[immutable] (val rootNode: MapNode[K, V], val cachedJavaKeySetHashCode: Int, val cachedSize: Int)
   extends AbstractMap[K, V]
     with MapOps[K, V, ChampHashMap, ChampHashMap[K, V]]
-    with StrictOptimizedIterableOps[(K, V), Iterable /* ChampHashMap */, ChampHashMap[K, V]] {
+    with StrictOptimizedIterableOps[(K, V), Iterable, ChampHashMap[K, V]]
+    with StrictOptimizedMapOps[K, V, ChampHashMap, ChampHashMap[K, V]] {
 
   override def mapFactory: MapFactory[ChampHashMap] = ChampHashMap